Would it ever be possible to make a synthetic hydrocarbon that wouldn't produce harmful by products.
I assume you mean when burned in oxygen. There will always be some product of the reaction. Carbon dioxide seems "harmful" in the sense that it is a greenhouse gas. I don't know what you can burn that won't produce CO2, but I'm no chemist. My question would be what products do you consider harmful?
Thermodynamically, CO2 is a desirable product of hydrocarbon combustion.
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